How do we know if an alloy contains aluminum?

To determine if an alloy contains aluminum, one can use various analytical techniques. A common method is spectroscopy, which can identify the presence of specific elements by analyzing the wavelengths of light absorbed or emitted. Another approach is the use of a spark test, where a sample is struck against a grinding wheel to produce sparks; the color and pattern of these sparks can indicate the presence of aluminum. Chemical tests, such as the reaction with sodium hydroxide, can also be used, as aluminum reacts with NaOH to produce hydrogen gas. Lastly, X-ray fluorescence (XRF) is a non-destructive technique that can accurately determine the elemental composition of an alloy, including aluminum content.